Current navigation systems are optimized for cars, not pedestrians. Pedestrians can often take routes which are not possible by car, e.g. indoors or small paths which are not easily visible on maps. In some cases, e.g. city centers, pedestrian maps also show paths for pedestrians, but this is not widely available in many areas. Even further, this typically does not include indoor shortcuts. This means that most of current map data is only suitable for outdoors and routes are only complete for car travel using GPS receivers. Moreover, GPS signals are adversely affected by multipath delay of the GPS radio signals when they are reflected off surrounding terrain; buildings, canyon walls, urban streets, hard ground, etc. Because GPS signals have a very low power level when they reach the Earth's surface, they are almost completely attenuated inside buildings.
Even though navigation data has become very comprehensive, one cannot assume that all possible pedestrian shortcuts are included in current navigation systems. It would be useful to enable pedestrians and others to create navigation data for their own use. Additionally, existing navigation systems are not operational for indoor use.